Optimize Battery Equalization System Design

With the rapid development of the socio-economic and industrial modernization, the depletion of oil resources and environmental pollution problems can not be ignored. In recent years, battery power is more and more widely used of in the field of new energy power generation, electric vehicles, space power, communications equipment, standby power as an energy storage device. Because the limitation of the technical constraints of battery manufacturing technology and battery management systems (BMS), In order to provide sufficient power supply voltage and driving power, we have to provide a large number of battery multi-level series-parallel. However, when these batteries is used in tandem, the cells is easily over charged and over discharged due to the unbalance problem of capacity. This problem greatly affects the cycle life and safety of the battery pack. Therefore, a kind of reliable and balanced circuitry and balanced strategy become a key technology to solve this problem. The most important task of this paper is to design a balanced system, which is good at precision, speed, efficiency, cost and other indicators.Based on a comprehensive analysis of domestic and international power battery balancing technology and research of the problems of traditional equalization techniques, an intelligent distributed lossless equalizer circuit is proposed. Every balanced sub-module of the circuit only requires one capacitor, which works as the energy transfer component, magnetic elements is used only as a protective component. Both the direction of energy transfer and the equalization effects of the neighboring cells can control by two MOSFET s.The balanced system which based the single chip MSP430F169had been designed as the key MCU (Micro Control Unit). The control module can implement these functions, including the switching logical judgment, producing the PWM signal as equalization control, high-precision data sampling, touch-keys control, fault detection and alarm.Firstly, according to the principle of the balanced system, the hardware design of each module in the equalization circuit is described in detail. Which introduces the calculation of the parameters, component selection and hardware implementation principle and so on; Secondly, C-based language is written to driver the balanced system and optimize the design of the each parts of functions, meanwhile, the software flow chart of each sub-module is given in the paper; Thirdly, the simulation circuit of the balanced module is built by MATLAB/SIMULINK. With the balanced strategy and balanced system parameters, equalizing process is simulated to verify the feasibility of the equalization scheme. Finally, the experimental platform consisted of three cells is established. Through testing, balanced accuracy is up to±10mV, the equalization has the advantages of fast balancing speed. So it is proved that the design has achieved the expected results between the three cells in the battery pack.Experiment and simulation shows that the structure is simple and safe. Beside that, the circuit is easy to achieve modularization. When equalization module uses in a large number of batteries, equalization system is low cost, easy alignment and suitable for the field of power battery application. This equalization technique provides an effective foundation for the balanced system with large-capacity battery pack and multi-level balanced structure.